The human immune system is highly complex and at present imperfectly understood. It is presently considered to have two principal aspects: (1) humoral immunity, which is mediated by circulating antibodies; and (2) cell-mediated immunity, which, as the name implies, is mediated by cells, viz., lymphoid cells. Humoral immunity is transferred from an immune donor to a non-immune recipient by means of serum immunoglobulins. Such serum-mediated transfers result in immune responses that are manifest almost instantly. Cell-mediated immunity is transferred by means of peripheral blood leukocytes, and such immune responses develop slowly, over a period of several hours. The present invention concerns cell-mediated immunity.
A typical manifestation of cell-mediated immunity is the delayed hypersensitivity ("DH") skin reaction. A DH skin reaction is observed when the appropriate antigen is injected subcutaneously. Within 24 to 48 hours, local inflammation (erythema) and a swelling and thickening (induration) are observed in a sensitive individual. The degree of sensitivity may be measured by the size and severity of the reaction. The DH reaction also presents characteristic histological findings, specifically, perivascular infiltration of lymphocytes and monocytes in the inflamed area. The cells seen at the site of a DH reaction are derived from the peripheral blood leukocyte population.
The mechanisms of cell-mediated immunity are as yet incompletely understood. It is known that the cells which mediate the response are capable of responding in a variety of ways to an antigenic challenge. These responses include: proliferation of cells bearing specific sensitivity to a given antigen; the induction and multiplcation of cells mediating a variety of immune functions, including antibody production; and reactions against foreign cells and tumors. The quality and quantity of these response patterns is affected by many factors, including (1) hormones of the thymus and adrenal cortex; (2) interferons; and (3) other effectors of cellular responses, including histamine, serotonin, and the prostaglandins.
The present invention relates to the discovery of modulators of the immunity system, isolated from dialyzed extracts of leukocytes; profoundly affecting the quality and quantity of cell-mediated immunity responses; useful in the treatment of a variety of clinical conditions characterized by overreaction or by inadequate reaction to a specific antigen; and useful in the alleviation of certain anergic conditions.